I am a complete noob when it comes to maya but i would like to change my player models and everytime i export models from BO2 they ain`t full body models and i`m completely clueless on how to join the head to the body correctly to work with WaW, if anyone could help me with this i would really like it. thanks in advance.

If you export the models from black ops 2, you should have "Dempsey_fullbody" and alike for the other heroes. Check again

Also there will be issues with BO2 models due to them having more joints. You will need to remove the additional joints or their faces will be screwed up

What HarryBo said, also attaching the head to the body is done via script in most cases.